Dear English teacher:
I have a question about the word “allergy”: Should it always be used in the plural form? For instance, can I say, “My allergy is getting worst” or should it always be “my allergies are getting worse”? What if I was referring to only one case?
I have heard people say “allergies?”(Always plural) when someone sneezes.
Except when it is used before a noun like, allergy season, food allergy and the like.
If you have a known specific allergy, you would proabaly refer to it in the singular. "I have a peanut allergy."
People who sneeze a lot usually are sensitive to various environmental factors, so it is usual for them to say they have allergies.